An element of the general type subject of the present invention is disclosed in Brenner et al, U.S. Pat. No. 4,650,680. Annular cylindrical cells of this type principally, because of the performance qualities of alkaline silver oxide/zinc systems are particularly desirable for probes and assistance systems utilized in the exploration of earth resources. In such explorations successively deeper earth layers must be explored and with increasing depth, the correspondingly increasing temperature becomes the deciding limiting factor in the components in the construction of the battery. It is known for example, that manganese oxide cells supplied with aqueous potassium hydroxide remain fully functional above 100.degree. C. in place of the Leclanche electrolytes used in conventional primary elements. A further advance having the goal of operating at the higher temperatures while minimizing the corrosive attack of the aforesaid electrolytes on the inner portions of the cell, was directed, in the aforesaid patent to the selection of resistance elements for the separator. The combination of ceramic paper and ion exchange membrane was found to be very useful.
Notwithstanding the provision of highly inert separators, alkaline manganese and silver oxide annular cylindrical cells having negative zinc electrodes, reach their operative limit at around 160.degree. C. The reason lies less in the qualitative inferiority of the electrochemically inactive cell components than the occurrence of explosions which were already noted in numerous cells on the third day during storage tests at 160.degree. C. The reason for these explosions is the substantial generation of gas at the zinc electrode, which occurs because the hydrogen over potential at the zinc drops with increasing temperature, which in turn give rise to an exponentially increasing rate of generation of gas.
It would be desirable to provide an alkaline primary element basically constructed in accordance with the known principles of construction of annular cylindrical cells and provided with an externally located positive electrode, which is modified in such a manner that it may be reliably utilized in the higher temperature ranges mentioned above without the possibility of excess gas generation.